Pity the Republicans. Defeated in the presidential election, depleted in Congress and departing from the White House in disgrace, they are a shell of their previously bullish selves. As much of the country, and indeed the world, celebrated the inauguration two weeks ago, they looked askance. It was unclear how many of them realised that one of the reasons this particular ceremonial theatre was so popular was because they were leaving the stage.

This weekend they held a conference in Washington entitled "Republican for a Reason", where it rapidly became evident that nobody was entirely clear what that reason was. Having set out as social conservatives, they ended up as conservative socialists - big spenders who made the first moves towards nationalising the banks.

The party elected Michael Steele as its national chairman. Promising outreach and renewal, Steele - the party's first African-American leader - claimed Republicans have an "image" problem. That's true. According to a recent Pew survey, the Democrats are enjoying the greatest favourability advantage it has ever recorded. Republicans trail in every demographic group apart from white evangelicals.

The problem with the party's image is that it is a faithful reflection of its policies and culture. Steele, who once compared stem-cell research to concentration camp experiments, was the moderate in the election. He defeated the South Carolina chairman, Katon Dawson, who became politically active in protest at racial integration of schools and was a member of an all-white country club for 12 years before leaving last year. It was a close run thing. Steele won 91-77 on the sixth and final ballot.

According to a recent Rasmussen poll, almost half of Republicans think their problem is not that they have been too rightwing, but too moderate. More than half think the Alaska governor and defeated vice-presidential candidate Sarah Palin offers the best model for their party. To the extent that they have learned any lessons from their defeat, they seem to be the wrong ones.

One of the few people prepared to give Republicans the time of day at the moment is President Barack Obama. For the past two weeks, Obama has been desperately trying to persuade them to support his economic stimulus package. After several trips to Congress for negotiations he called on Democrats to strip some elements from the bill that Republicans objected to. He also added more of the tax cuts they wanted.

Why he would go to such extraordinary lengths is baffling. He's well aware of who's in charge. During one of his first meetings, he responded to one criticism from the Republican whip by saying: "We just have a difference here, and I'm president. So I'm going to prevail on that." And people are far more keen on him prevailing than them. According to Research 2000, Obama has an approval rating of 75%. Meanwhile, fewer people have even heard of the Republican minority leader of the Senate (Mitch McConnell) or the House (John Boehner) than approve of the job they are doing.

Nonetheless, despite being courted and indulged, when the stimulus plan came to the floor not a single House Republican voted for it. Later that evening Obama invited some of those Republicans over for cocktails and started the wooing all over again.

Alongside invoking God, patriotism and the spirit of the founding fathers, every presidential candidate pledges to reach across the aisle, dampen partisan rancour and put the interests of the voters first. But this was particularly true for Obama, who pledged a different, more consensual, approach to politics in Washington.

Bringing more civil and constructive engagement to politics is, as a means to an end, a perfectly laudable goal - particularly after eight years of crude majoritarianism. Democracies are not elected dictatorships. They should be places of discussion and debate, compromise and consensus.

But while it makes sense as a process, as a principle bipartisanship is worthless, since it depends entirely on who you are engaging with and to what purpose. The war in Iraq, the war on terror and the deregulation of the economy were all bipartisan efforts. All have been disastrous.

Many Democrats went along with these things not because they thought they were good for the country, but because they believed that not to do so would be detrimental to their party.

Indeed, far from elevating the interests of the country above the party, bipartisanship mostly achieves the opposite - suggesting that the principal aim of policymaking is consensus among the political elite rather than delivering for the electorate. The fact that the political class comes together in a cordial manner to support something does not in itself make that thing good.

The problem that has plagued Washington over the last few years is not "partisanship" that supports one idea or another, but a more sectarian "partysanship" that supports the interests of one party over an idea. The problem with George Bush was not that he did not listen to anybody else's ideas, it was that his ideas were terrible.

Viewed in this light, the Republican response to Obama's overtures makes a grim kind of sense. Given the ballooning budget deficit and failure of tax cuts under their watch, the Republicans have no ideological integrity. So in the absence of a clear alternative or coherent leadership, they have decided to distance themselves from the entire project. They have calculated that if the stimulus package works, Obama will get the credit anyway. And if it doesn't, they don't want to be associated with it. It's not constructive - but it is at least politically cogent.

It is the overtures themselves that are bewildering. The burning priority for Americans at this juncture is not that their two main parties work together. It's that their government does something to revive the economy. The concessions Obama has made to the Republicans have actually made that outcome less likely. Virtually every reputable economist agrees that the most effective way of pumping money into the economy quickly, in order to create jobs, is through public spending. Individual tax cuts are more likely to be saved, and business tax cuts take a long time to take effect.

As the economic stimulus bill goes to the Senate for negotiation, there is a real possibility that Obama may end up with the worst of all worlds: an inadequate stimulus package that has been watered down by the Republicans; a huge budget deficit; and still no support from the Republicans.

What the Republicans fear is precisely what many Democrats hope for: paradigm-shifting legislation that rolls back some of the excesses of the last generation by returning government to the centre of American public life, creating jobs and uplifting the poor, while extending healthcare and educational opportunities to working-class families.

"Never let a crisis go to waste," said Obama's chief of staff, Rahm Emanuel. This economic crisis has given the president the opportunity to do for the poor what 9/11 gave Bush the chance to do for the oil companies. When capital is in such short supply, he shouldn't squander it on a sub-prime party.